Supporting multiple organometallic catalysts on poly(norbornene) for cyanide addition to α,β-unsaturated imides

A two-catalyst system comprising of salen(AlCl) and pybox(ErCl₃) complexes supported onto poly(norbornene) has been developed. As a proof of concept the activity of the two-catalyst system was gauged for the addition of cyanide to α,β-unsaturated imides which has been shown to follow a bimetallic mechanism. The activity of the supported two-catalyst system was significantly higher than catalytic systems derived from mixtures of the two catalysts. In addition, the co-polymer could be readily recovered and reused up to 3 cycles without significant loss in conversions and yields. Nevertheless, a decrease in enantioselectivity of the cyanide adduct was observed with each subsequent cycle indicating some loss in catalytic selectivity. The reported strategy opens up avenues for supporting multiple catalysts on the same polymer backbone for catalyst-based one-pot cascade reactions.